1. Field of the Invention
This invention relates to an improvement in a stationary electromagnetic induction unit such as a transformer of low voltage and high current for a rectifier or an electric furnace, for example.
2. Description of the Prior Art
FIGS. 1 and 2 show a shell type transformer (hereinafter merely referred to as a transformer) for a rectifier which is a conventional electromagnetic induction unit. FIG. 1 shows a structure of an iron core and a coil. FIG. 1(a) is a section in plan taken on line Ia--Ia of FIG. 1(b), and FIG. 1(b) is a section in side taken on line Ib--Ib of FIG. 1(a). FIG. 2 is a perspective view of a copper plate coil constituting a low voltage winding. In these figures, reference numeral 1 denotes a shell type core, and 2 a high voltage winding. Two plate-like high voltage coils 3 and 4 are connected in series (not shown). Reference numeral 5 denotes a low voltage winding, and four copper plate coils 6 to 9 are connected in parallel. Each of the copper plates coils 6 to 9 is a rectangular plate-like coil in which a bare copper plate 10 having a conductor width W is wound into an edgewise wound coil of one turn. Four copper plate coils 6 to 9 are connected in parallel by connection conductors (not shown) at connection leads 10a and 10b of each bare copper plate 10.
Each of the copper plate coils 6 to 9 has a shape in which a single copper plate 10 is wound edgewise as described above and is not divided in a direction of the conductor width W of the copper plate 10. Therefore, a large stray loss occurs due to a leakage flux vertically interlinked with the surface of the copper plate 10 (As is known, an eddy current loss is proportional to the square of the conductor width W when the magnetic flux vertically interlinks with the surface of the copper plate). This poses problems that make the efficiency of the transformer low, the capacity of the cooler large, and so on.